W8???

Sharky · 22 Apr 2001, 14:46 (Ref:83576)

Well, I was just reading this month's edition of Motor Trend and there was a small remark on the new VW Passat. The thing that grabbed my attention was that it has a W8 engine. Now, I'm not surprised about the W configuration. After all, It's been quite some time since Audi isplayed their W12 engine and we all know about the insane Buggati W 18 but, isn't every "bank" in the engine supposed to have the same ammount of cylinders?? Just like in a V engine the engine has to have a multiple of 2 number of cylinders, shouldn't the W engine have a multiple of 3 number of cylinders?. Or do they use a 2-4-2 configuration or something like that?

Marshal · 22 Apr 2001, 17:32 (Ref:83640)

Yeah, I wondered about that too, but VW do make a V5 three on one bank two on the other. Just don't ask why, 'cos it makes no sense to me.

Sharky · 22 Apr 2001, 20:49 (Ref:83738)

Well, I do recall that there were 5 cylinder Audis but I always thought they had a 5 in line configuration. The appearance would be kinda odd....

chtan · 22 Apr 2001, 21:31 (Ref:83771)

well, the W format used by VW has 4 cylinder banks. hence the W8 has a 2-2-2-2 configuration and the W12 a 3-3-3-3 config. if I'm not mistaken, the W12 started as two narrow angle(about 18 degrees) V6 engines joined at the crank. and VW also makes a V5..... I also thought that each bank must have the same number of cylinders.. can anyone explain how the number of cylinders per bank affects the balance of the engine?

Sharky · 23 Apr 2001, 02:13 (Ref:83871)

But I recall seeing a pic of the Audi W12 engine block and it consisted of 3 four cylinder banks. However I have this pic of the buggati engine and it clearly has 4 banks....mhhh....now I'm confused because. I know the audi engine has 3 banks......I have the pic right here but.....

Marshal · 23 Apr 2001, 09:33 (Ref:83947)

Quote:

Originally posted by chtan
well, the W format used by VW has 4 cylinder banks. hence the W8 has a 2-2-2-2 configuration and the W12 a 3-3-3-3 config. if I'm not mistaken, the W12 started as two narrow angle(about 18 degrees) V6 engines joined at the crank. and VW also makes a V5..... I also thought that each bank must have the same number of cylinders.. can anyone explain how the number of cylinders per bank affects the balance of the engine?

I think that a W has 3 banks (as shown in the picture of a W12), four banks of cylinders are usual known as an H or an X, depending on exact configuation.

KC · 23 Apr 2001, 16:15 (Ref:84039)

Its not unheard of to produce engines with uneven number of cylinders in each bank. Honda's new GP bike engine is reported to be a 5 cylinder Vee engine to improve packaging.

I would imagine an 8 cylinder engine could be made to be as long as three cylinder engine with two outer banks of three cylinders and an inner one of two. An engine can be made to sit cross ways in a smaller cars engine bay for a front driver setup. It also allows the designer to engineer more cabin space for passengers by reducing engine bay size while maintaining car size.

The only concerns I see are NVH (Noise, Harshness and Vibration) damping, engine cooling and maintenance issues.

Dino IV · 24 Apr 2001, 04:06 (Ref:84283)

Quote:

Originally posted by Sharky
But I recall seeing a pic of the Audi W12 engine block and it consisted of 3 four cylinder banks.

You got a bit confused by Volkswagen marketing. They dropped the "R" in i.e. VR6. So the successor of the old Golf III VR6, with exactly the same engine, now is being sold as the Golf IV V6. Along the same lines the Golf V5 is actually a VR5, so the same block as the VR6 minus one cylinder. As you probably know the VR6 concept consists of two cylinder rows at V angle 15 degrees in the same engine-casing thus looking like a wide but short 6-in-line. Apparentely their modular design has worked out so well they can even produce VR4, because the Passat W8 consists of two VR4 cyilinderrows at a V angle of 72 degrees.

Sharky would cause a huge stir if he comes up with a pic of Audi (which is the same company as Volkswagen) W12, because this engine consists of two VR6 cylinderrows at an angle of 72 degrees.

A real W-configuration exists of 3 cylinderrows spaced at equal angles. At each throw of the crankshaft there are three conrods attached. Like the Bugatti W18 on show here. It doesn't have four banks, but three and the block is tilted to the right with all the extra gear (starter, alternator etc) to the left. Three 6-in-line cylinderbanks spaced at a guessed 60 degrees apart (central power output clearly visible).

The so-called W-configuration is actually a Double V-set-up because it consists of two cylinderrows close together or in the same bank like the VRx, one wide main V-angle, and the other bank, similar to the first one. Like the W8 or W12. 15 + 72 + 15 degrees. At each throw there are two conrods attached. It would have been clearer if they would have called it a Double V or V-VR or something instead of W.

Totally off-topic:

Quote:

Originally posted by KC
Honda's new GP bike engine is reported to be a 5 cylinder Vee engine to improve packaging.

For packaging they'd stick to their SBK twin as it is today.

That V5 (no VR5, but really a 3 cylinderbank angled with a 2 cylinderbank) is being tested for next year's rule changes where four strokes are allowed bigger displacement (as opposed to 500 cc today, that's why everyone runs 2 strokes) and different configurations. The 2002 rules are in brief:

Displacement:
4-stroke: max. 990cc
2-stroke: max. 500cc

Minimal weight:
4-stroke, 2/3 cylinders: 135kg (or 145kg with oval pistons)
4-stroke, 4/5 cylinders: 145kg (or 155kg with oval pistons)
4-stroke, 6 or more cylinders: 155kg
2-stroke, 4 cylinders: 130kg

Fuel limit:
4-stroke: max. 24 liters (22 liters from 2004)
2-stroke, max. 32 liters

So the 5 cylinder 990cc engine will allow them to search for highest revs at the relatively low 145 kg. They'd probably bet on antother horse or two, entering the big SBK-twin and the NSR 500. Moto GP really looks like an awesome engineering challenge for the seasons to come.

Izzy · 24 Apr 2001, 07:56 (Ref:84334)

Quote:

[i]Or do they use a 2-4-2 configuration or something like that? [/B]

Wouldn't it be a 3-2-3 configuration

Sharky · 24 Apr 2001, 17:21 (Ref:84483)

Well, taking a closer look at the Buggati engine. It's true what you say about it being only 3 banks. However, havin an asymetrical engine like that doesn't cause some kind of imbalance or something of the sort.

BTW, I have the pic of the W12 Audi engine in my hands. theres the pic of the full engine and just the block. (don't have a scanner though) and it clearly has 3 for cylinder banks separated at some 40° from each other from what I can see in the picture. The caption reads "...the latest proposal from Audi, with it's brand new machine with 12 cylinders in W configuration". The magazine is old thogh. July 27 1994.

Dino IV · 25 Apr 2001, 00:13 (Ref:84603)

The Bugatti W18 could be seen as three 6-in-line engines which are perfectly balanced in their own right - like they are in for instance BMW's. The center power transmission is also pointing at a lot of effort in achieving balance.

About the Audi W12 picture: you're eyes are not deceiving you. That is an three 4-cylinder bank real W-configuration and an Audi as well. That was the engine feautured in their Audi Avus prototype from 1991 or 1992. You probably recall it. It was that 'chrome' mid-engined sportscar with 20+ inch wheels and high rear mirrors. Maybe I can find a picture of it. Ah, here it is:

Their new W12 in the Audi A8 is the double VR6 as mentioned before.

Sharky · 25 Apr 2001, 01:34 (Ref:84616)

Yeah. I recall reading about the Avus having the W12 engine. But while I looked for the pic of the W12 engine I did come across several pics of the "new" W12 that comes in an audi A8 (If I'm not mistaken) and a prototype by VW that, as you said, consist of 2 VR6 engines. I would guess that they don't share the same crankshat, then, what advantages would you get from a 2 engine configuration instead of a regular V12 or W12 like the one in the avus?

Sharky · 25 Apr 2001, 01:44 (Ref:84619)

Here's a pic of the "new" W12 engine BTW.

Ray Bell · 25 Apr 2001, 01:56 (Ref:84624)

That's not the traditional 'W' configuration, is it?

The description of single-bank staggered-bore engines as Vees is a bit confusing in my opinion. And I wonder about the block mass...

As for the 'W' description for three-bank engines, the better description is 'broadarrow', but that's too cumbersome...

Dino IV · 26 Apr 2001, 03:46 (Ref:85155)

Staggered-bore. Tnx Ray, that was the word I was looking for. I didn't came up with anything better than 'slalomming'.

The advantages of the Audi's VV12 compared to a V12 is its shortage. It's almost like a V12 which has been crunched by a benchpress. But as Ray says there's a optimum to what angle you can stagger the bores, the shorter the bank gets and the mass of the single bank not becoming too big and I guess Volkswagen has already figured that out with their 15 degree angle in the VR6.

The disadvantage of the traditional W12 is weight (because three banks is always more than two banks even if they are staggered-bore) and height (because the upright bank, well is .. upright

).

Audi has put a lot of effort in reducing the weight of the VV12. It even has a dry-sump system which should be a first for a limo-engine, isn't it?